Ya this reminds me that I've been using Menu-Toolbar kind of UI for long long time. And subsequently this model applied by almost all non-Microsoft applications. And now we can even see this UI model on the Web pages.

I like the answer given by Larson-Green, the group program manager at Microsoft in the
interview:
It’s important to note that the new UI is not intended to be a general-purpose application model. It’s not a replacement for menus and toolbars for all applications. There’s nothing wrong with menus and toolbars. It’s just that our powerful authoring applications have lots of commands, so we needed a different model –a higher-level way of presenting commands.
Wonder if Mustang (Java SE 6) would follow this footstep, I hope so.